When you have to look in thick rough, long grass, bushes or other questionable areas in order to find a ball, the Rules give you a lot of leeway. You can move and bend stuff, but there is one key thing you cannot do:
A fair search actually includes a lot you might normally not be allowed to do around the ball. You may move or bend long grass, bushes, tree branches and other growing or attached natural objects. You may even move sand and water to find the ball. In general, your searching should not change the situation of the ball, but so long as you are fairly searching, even if the conditions affecting the stroke are slightly altered, that’s ok. There is one change that must be corrected: